title: Regulation of type VI secretion gene clusters by sigma54 and cognate enhancer binding proteins.
abstract: Type VI secretion systems (T6SS) are bacteriophage-derived macromolecular machines responsible for the release of at least two proteins in the milieu, which are thought to form an extracellular appendage. Although several T6SS have been shown to be involved in the virulence of animal and plant pathogens, clusters encoding these machines are found in the genomes of most species of gram-negative bacteria, including soil, marine, and environmental isolates. T6SS have been associated with several phenotypes, ranging from virulence to biofilm formation or stress sensing. Their various environmental niches and large diversity of functions are correlated with their broad variety of regulatory mechanisms. Using a bioinformatic approach, we identified several clusters, including those of Vibrio cholerae, Aeromonas hydrophila, Pectobacterium atrosepticum, Pseudomonas aeruginosa, Pseudomonas syringae pv. tomato, and a Marinomonas sp., which possess typical -24/-12 sequences, recognized by the alternate sigma factor sigma 54 (σ(54) or σ(N)). σ(54), which directs the RNA polymerase to these promoters, requires the action of a bacterial enhancer binding protein (bEBP), which binds to cis-acting upstream activating sequences. Putative bEBPs are encoded within the T6SS gene clusters possessing σ(54) boxes. Using in vitro binding experiments and in vivo reporter fusion assays, we showed that the expression of these clusters is dependent on both σ(54) and bEBPs.
authors.affiliation: Laboratoire d'Ingénierie des Systèmes Macromoléculaires, Institut de Microbiologie de la Méditerranée, Aix-Marseille Université, CNRS-UPR9027, 31 chemin Joseph Aiguier, 13402 Marseille Cedex 20, France.
authors.forename: Christophe S
authors.initials: CS
authors.lastname: Bernard
authors.forename: Yannick R
authors.initials: YR
authors.lastname: Brunet
authors.forename: Marthe
authors.initials: M
authors.lastname: Gavioli
authors.forename: Roland
authors.initials: R
authors.lastname: Lloubès
authors.forename: Eric
authors.initials: E
authors.lastname: Cascales
mesh_terms: D001419:Bacteria / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D019295:Computational Biology; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology; D005810:Multigene Family; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D051877:RNA Polymerase Sigma 54 / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins; D013045:Species Specificity; D014158:Transcription, Genetic
chemical_list: D001426:Bacterial Proteins; D011994:Recombinant Proteins; D051877:RNA Polymerase Sigma 54